Whilst The Far Slayer is very heavy and has no magical properties (unlike Sun's Messenger, which slays undead), it is nonetheless an extremely powerful missile weapon and is by far one of the most powerful missile weapons in the game. Whilst its base stats of (+18, +18) makes it technically the best missile weapon, whether or not it would be more desirable for a PC than Sun's Messenger in practice usually depends on a number of factors — e.g. the PC's skill levels in bows and crossbows, or if the PC needs to exterminate a lot of powerful undead creatures (which any arrow fired by Sun's Messenger can do with relative ease).

Like all random artifacts it can be granted as a precrowning gift or a reward for making use of a potion of uselessness; generated in a surge of power or greater vault; or generated as random loot (albeit very rarely).

---------------------------- heavy crossbow------------------------------
The heavy crossbow is actually a blessed heavy crossbow "The Far Slayer"
(+18, +18).
It is an artifact.
When used in melee combat it grants a -3 bonus to hit and causes 1d6
points of damage. When used as a missile it grants a +18 bonus to hit
and causes 1d3+18 points of damage.